Field of the Invention
The present invention relates generally to a focusing apparatus, and more particularly to a focusing apparatus configured to provide a zoom tracking control that moves a focus lens to an in-focus position along with a zooming operation.
Description of the Related Art
Many conventional video cameras etc. can provide a so-called zoom tracking operation configured to move a focus lens to a (supposed) in-focus position when a zooming lens is moved for zooming. The zoom tracking operation moves the focus lens along a cam locus curve stored in a memory for a corresponding zoom lens position.
The memory needs a high capacity to store cam locus curves at any object distances for the zoom tracking operation at the current object distance. Thus, the memory stores only a plurality of referenced cam locus curves corresponding to a plurality of referenced object distances and a cam locus curve at a non-referenced object distance is calculated through interpolation processing.
Japanese Patent Laid-Open No. (“JP”) 6-121212 discloses a method for calculating a non-referenced cam locus curve using one referenced cam locus curve so as to reduce a data amount to be stored in the memory.
However, simply using the referenced cam locus curve disclosed in JP 6-121212 cannot fully correct individual scattering of a lens and a barrel and a spherical aberration etc. at a non-referenced object distance, and would deteriorate the tracking performance.
JP 6-121212 discusses an interpolation method of a cam locus curve but is silent about a correction of an aberration etc. at each object distance.